RETROCESSION (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Ceded Credit Risk [Line Items]
Premiums ceded to other companies									$ 33,800,000	$ 10,900,000	$ 9,800,000
Loss and loss adjustment expenses incurred, net	$ 122,658,000	$ 168,918,000	$ 106,016,000	$ 104,812,000	$ 97,304,000	$ 81,467,000	$ 111,376,000	$ 90,668,000	502,404,000	380,815,000	317,097,000
Loss and loss expenses recovered and recoverable									31,800,000	900,000	1,700,000
Loss and loss adjustment expenses recoverable	29,459,000				2,704,000				29,459,000	2,704,000	$ 3,368,000	$ 11,523,000
Funds withheld from unrated retrocessionaires	23,579,000				5,927,000				23,579,000	5,927,000
Collateral Held in Trust	377,900,000				86,400,000				377,900,000	86,400,000
Provision for uncollectible losses recoverable	0				0				0	0
AM Best, A- Rating [Member]
Ceded Credit Risk [Line Items]
Loss and loss adjustment expenses recoverable	3,100,000				500,000				3,100,000	500,000
Unrated [Member]
Ceded Credit Risk [Line Items]
Loss and loss adjustment expenses recoverable	$ 26,300,000				$ 2,200,000				$ 26,300,000	$ 2,200,000